Abrasive projecting apparatus



Sept. 7, 1943. N. J. Q'UINN 2,328,581

ABRASIVE PROJECTING APPARATUS ATTRNE'YS.

Sept. 7, 1943. N- J, QUINN 2,328,581

ABAsIvE PRoJEcTING APARATUs INVENT OR.

i /VELsoNlQu/NN BY'! ATTORNEYS.

Sept. 7, 1943. N. J. QUI-NN ABRSIVE PROJECTING APPARATUS Filed Nov. 8.,1940 4 Sheets-Sheet 3 INVENTOR. NELso/v \.7.` Qu/NN ATTORNEYS; 1

Sept. 7, 1943., N. J. QulNN ABRASIVE PROJECTING APPARATUS 4 Sheets-Sheet`4 Filed Nov. 8, 1940y INVENTOR. NELSON JIQu/N/v BY @/Mmy lAVroRNEx/s..v4

Patented Sept. 7, 1943 U N I T E D STATES P-ATEN T OFFICEABnasIvr-LPROJECTING APPARATUS Nelson it. Quinn, Toledo, 'ohio yApplication November 8, 1940, Serial No. '364,931

(ci. s1- 8) 25 Claims.

This application is a continuation in Apart of my co-pending applicationSerial No. 166,082, for Abrasive projecting apparatus, led September 28,1937.

The present invention, relating -as indicated, to a method of andapparatus -for projecting abrasives, is more particularly directed -toIa method of and apparatus for projecting successive charges ofabrasiveiat a high speed by means of uid pressure released in smallincrements or charges to reduce the consumption of the same and produceexplosive-like pro-pulsion of the abrasive charges against the Work. Afurther'vobject of the invention is the provision of a method andapparatus that will reduce the costof abrasive cleaning and increase theeiiiciency. Another object is the provision of a simple Vand inexpensivemechanism forcarrying out the method referred to above and one that willhave a minimum ci' working parts and greatly reduce -the destructive andrapid wear of the abrasive -on the propelling mechanism.

The cleaning of castings `is, today carried outlay 4three methods, (l)tumbling, (2) propelling abrasive against them by feeding the same intoan air `blast and (3) directing abrasive against them by a centrifugalwheel. 'Tumbling is ,slow and `applicable only to certain types lofcastings. .An air blast is extremely wasteful `ef air and -a vrelativelysmall amount of abrasive can be carried by the air stream. CentrifugalWheels are a development, commercially at least, of the last few yearsand. while very effective are expensive to maintain because of the highWear o-n the blades and means for feeding abrasive to the blades. Inaddition the propulsion speed of abrasive thrown by a wheel must be keptmuch lower than from an air blast to prevent excessive wear on theblades and to `avoid still other difficulties in operation. The presentinvention provides a method and apparatus the cleaning operation ofwhich is more efiicient than any of those now in use.

As will be hereinafter `more particularly explained, my projectingapparatus has been designed to be operable entirely by means o-f asingle supply of compressed air, which acts also a's the propellingagency for the slugs of abrasive. Other features and objects of myinvention will appear from the detailed description following asconstrued in the `light of the drawings appended hereto. The novelfeatures of the invention will be summarized in the claims.

Referring now to the drawings: y

Fig. l is a longitudinal cross-section of one form of my abrasiveprojecting gun;

`a convenient distance away from the device.

fFig. 7;

A9 is .a sideeievat'ion of one of demente, of the device seen 'in Fig.v5;

Fig. -1'0 .is a side View Aof f another element ofthe .device seen inFig. 5,; l

Fig. 1l is a side elevation partially in section of another alternativeform of my abrasive projecting gun; and

Fig. 12 is a 'fragmentary cross-sectional View taken substantially onthe Vline TI-l2 'of Fig. '11.

In general, my `invention may be said to 'comprise three parts; one, asuitable form of the air metering valve T5 two, 'the 'feed valve "for'abrasive I6; `and three, the barrel mechanism I1. These parts arebolted together to form a continuous unit and supplied with compressedair whichnot only furnishes the propelling 'forcefo'r the vabrasive vbutcontrols the operation of the device.

Air is -admitted to 'the metering chamber through a compressed airnipple |`8 and thence metered by the reciprocating piston I9, afterwhich it passes through the chamber '2'0 .into contact with theabrasive. l

In operation the metering .piston I9 lies horizontally, but vforconvenience is described as 'it appears in Fig.. l... It circular incross-section and is provided withthree annular recesses `2 I, 22 andI23 (Figs. l and 4). The recess 22,'whenpos'itioned in line with 'thenipple It andthe .passage 420 permits passage of the 'air `column to theabra sive feed chamber. The feeding `of air is Vcut off when the annularopening 22 occupies the posiftionshown in Fig. l, at which time it isout off Vline with the aforesaid openings. Piston lil i's reciprocablycarried in a chamber of the casing of the valve 15 and normally retainedin the posi- 'tion in Fig. l by suitable spring mechanism hereafter tobe described.

Reciprocation of the piston I9 is controlled lby an auxiliary line `25which meets the main lin'e fat In practice, I have Afound six feet to beay good distance as this revents surging in the main feed line frombeing transferred to the auxiliary line and affecting the control of thepiston i9. A needle valve 2l is inserted in the auxiliary line tocontrol the amount of air passing therethrough. As the auxiliary aircolumn leaves the needle air valve 2l, it enters a jacket integral withthe chamber of the valve i5, as shown in Fig. 4. Openings lead from thejacket 23 to the interior of the piston chamber. Valvel rings 35 carriedslidably in the openings 2l and 23 serve to open and close the intakeports til. Abutting pins 38 carried by the piston iS prevent the Valverings 35 from forming a seal against the flanges acting to limit theirmovement.

When the piston is in the position shown in Fig. 1 the lowermost valvering has been pushed down by the upper flange of the opening 2l to aposition opening the adjacent intake ports 3B. Air rushes through theports from the auxiliary line 25 filling the chamber formed adjacent therecess 2l and as a suitable pressure is built up, forces the piston i9upwardly (as shown in this figure) to bring the annular opening 22 inline with the nipple IS and the passage 2G. At this time a charge of airunder a pressure of approximately 6() to 100 pounds per square inchgauge rushes through the metering valve into the abrasive feed chamberto'propel the abrasive as hereafter described.

The action of the piston iS in opening the port 22 moves the lowermcstvalve ring 35 (as appears in Fig. 1, upwardly) to close the intake portsall and open exhaust parts it discharging to the atmosphere.Simultaneously the upper valve ring has closed the upper exhaust portsAlt and opened the upper intake ports 30. Air then enters the upperintake ports from the auxiliary line 25 and in the manner alreadydescribed forces the piston back down into the position shown in Fig. 1,closing the main air feed line to the abrasive feed chamber. As thepiston l is forced downwardly to this position, the valve vrings 35position themselves to again force the rpiston lll upwardly repeatingthe operation of feeding air intermittently to the abrasive chamber'.

Each time the piston it is forced upwardly in Fig. 1, mechanism isoperated to feed a corresponding amount of abrasive into position to bethrown through the barrel il'. This mechanism is best shown in Figs. 1,2 and 3. As there shown upward movement of the piston i9 forces thevalve pin 45 upwardly against a stiff compression sprinCf 4l which, inturn, rocks the rocker arm 59 about its pivot 5l. This movement, inturn, forces the valve pin E5 downwardly against the action of acompression spring 5l to reciprocate the valve plug 6l) integral withthe pin 25. As the plug 5l) is shifted, abrasive is fed to the ejectingbreech A suitable supply of abrasive is normally fed to the funnel lll'through which is falls to ll the chamber 63. As the plug te is shiftedby the piston i9, it assumes the dotted line position shown in Fig. 3 toclose off the funnel 6l and at the same time pack the abrasive charge inthe breech 65. It will be noted that a layer of abrasive stands betweenthe radial face of the plug and the breech, preventing wear on the plugresulting from the air column throwing the abrasive from the barrel.Similarly, the position of the plug closing the feed funnel prevents theair fed from passing up through the funnel Si.

As the piston IS moves to the position shown in 1 Fig. 1, the spring 51forces the plug SB outwardly and rocks the arm 50 to push the pin 45against the piston I3.

If desired, I could employ this spring action to return the piston toits inactive position.; although from the standpoint of better timing, Iprefer to make use of the double valve ring mechanism heretoforedescribed.

To prevent the abrasive moving either way from the breech zone I mayprovide radially split diaphragme lll, preferably formed cf rubber orother suitable resilient material and positioned as shown. The pressureof the air ejecting the abrasive is sufficiently strong to easilydisplace the diaphragms during the ejecting operation. As the first ofthe column of the compressed air passes the passage Eil, through theadjacent diaphragm 10, il; encounters the abrasive just deposited intobreech d5 and blows the same the mass of abrasive in line with thebarrel through the second diaphragm 'l0 and out the barrel l 'l as acompact slug.

It is a very important characteristic of my invention to eject thecharge of abrasive as a ccm- -pact slug and not intermingle relativelywidely separated particles of abrasive in an air stream asis done in theordinary type of air blast.

The barrel I7 as shown in Figs. l and 2 is surrounded by an outer shell'l5 and is preferably made of very hard cast iron to resist as well aspossible the abrasive effect of the charges shot therethrough. Even withthe hardest material now known, the barrels wear very rapidly and mustbe continually replaced. The same is true of the breech portion 55 andin lesser degree of any other portion of the machine handling abrasive.

To eect ready interchange of parts due to this wear, the device is builtin sections. As shown in Fig. l, the valve is provided with a ange 'I8Which is bolted to a similar iiange 8D carried by the abrasive feedvalve mechanism lli and which clamp between them the adjacent diaphragmlll. At the other end of the abrasive feed mechanism are similar flangesST2 which are bolted to corresponding flanges iid securing the barrel tothe rest of the device as shown. Similarly, the flanges S2 and S4maintain the adjacent diaphragm I9 in place and position a member with aconical opening adjacent the barrel to permit room for displacement ofthe adjacent diaphragm.

The plunger or plug member Ell wears very rapidly due to intimatesliding contact with abrasive fed to the breech and is readily replacedby removal of the cover 8l'. A shield 9@ is mountled on the outer barrelmember i5 adjacent the end to deflect abrasive bouncing back from thethe pressure of the spring 4'. will, if increased,

tend to move the plug Eil to open the funnel 6l more rapidly and furtherwill aid the air from the auxiliary line in returning the piston i9 toits initial position.

It will be seen from the foregoing description that I have provided anew means of projecting abrasive onto surfaces to be cleaned. By theterm abrasive I means any material of granuassegni jlar nature whichit`is desired to'project onto an object. It will further vbe -apparentthat my device projects such abrasive "in-'compact slugs as'distinguished from mixtures'of air and scattered abrasive, with theresult that very much less 'air is used for a given amountofabrasivethrown. 'Afurther 'result is that vthe abrasive vis projected'with much more force yonto the surface desired because of its compactnature, and because the particles travel under the momentum giventhemjby the force of the ejection. `It will also be apparent thatmy deviceis operable entirely from Vthe Vsingle column of air used to provide thepropelling force and that each mass or `slug of -abrasive is propelledahead of an vair column and through comparatively still air. l Thevarious 'parts of therdevice are automatic in operation. The yentireassembly is simple Ain construction and readily disassembled forcleaningand for "replacement due to wear.

The modification seen `more particularly yin lFigs. 5, 6, and 7comprises, in general, -a recepta- "cle 95 for receiving abrasive, areciprocating {irjing rtube 95 which projects -into the `receptacle andsegregates a slug of abrasive withinlthe -receptacle, a valve indicatedgenerally by the refverence character 91 forc'ontrolling admissionlo'f`fluid under pressure to the firing tube, a barrel 9B for directing theslug after the same is blown 'out of the firing tube, and a source ofpower 99 for reciprocating the firing tube and'actuating'the valve.

'I'he receptacle 95 is cylindrical and is pro- `vided with a vsuitableintake l|0| and an expan- 'sion chamber |02.

as 'the front end of the device, the receptacle is provided with a frontflange v|04 anda re'arfilange 105, the purposes of which `willhereinafter appear. f

The ring tube which, as `is above noted, is reciprocable within thereceptacle and is made of suitable wear-resisting material. Forfacilitat- 'ing the cutting or segregating of a'slugof abrasive, thefront end of the firing tube -is interiorly chamfered as at |01 to makeit sharp or, `if -dey,

-sired, the same may be exterior-ly chamfered. This is seen in Fig. 6.The rearend |08`ofthe ring tube threadingly lengages the valve, 'thelatter being part of the firing tube reciprocating means.

This valve will now be-describedin'detail, `reference being had moreparticularly to'Figs. `6 and '1. `A cylindrical valve casing |-|0 isprovided with 'a transverse wall Y|| so as to present a front chamberWhichissupplied'with compressed uid from-a flexible conduit ||2. Thefront end of Athe casing is interiorly recessed foraccommodatinganannular valve seat |-l'4 which -isretained 'therein by an exteriorlythreaded `nut -`|'|5, and

which presents a forwardly extending interiorly v'threaded nipple forengaging the threads ofithe end |08 of the firing tube.

Adapted for coaction with the valve seat |`|f4 is 4the head ||1`of avalve, the stem H8 kof which is slidingly engaged by an apertured bossH9,

With reference to thebarrel I *valvefthe vrear-end of @the stem 'H8 visProvided 75 'SCTCWS -being provided with a set screw 134. -lar actuatesthe valveopening means heretofore referred to.

Vbolted or otherwise secured lto -the lplate |28.

provided with a detent |45. lried by the plate v|42 is -a screw, `thebottom lof lthe valve casing and the firing tube. found 'that verylittle power is required to rotate 'is projected-out of the barrel 98.

lwith a slot |23 -w'hi'ch cooperates withfmeans *hereis provided Withacentral aperture for slidingly engaging the firing tube 96. @ne end o'fa pair of cylindrical slideways |121 -isvof reduced diame- Ater and isaccommodated by an opening ln'the plate |25 and secured in such opening`,by set The otherendof each of theslideways is similarly connected to aplate 428. Bolted vto the 4casing Il) `and slidingly engaging theslideways |21 is a pair Vof slideblocks |30 (see -Fig).

ner similar to that in which theslide'ways '|21 are 'connected thereto,-is a spacer rod 1| 32 rwhich slidingly `accommodates `a `collar |33,the :latter This col- -Such valve opening meanscomprisean arm 135 whichprojects through the slot `|23 offthe stern '|`|'8. As is more-clearlyseenin Fig' the upper -end of thisarm sadapted 'forengaging the col--'lar f| :i3-and the lower end of `thisarrn pivots-about forcesaretransmitted for reciprocating thecasing and the firing tube.

For imparting such reciprocating forces, fthe source of power "99,heretofore mentioned, -is provided and is, by way of illustration, `anyelectric motor suitablymounted on a-plate |42, `the latter beingpivotally vcarried byva plate H3 which is A vertical plate `|44. issecured to one side, asis seen in Figs. 5 and 6, of the centerof platemlandis Threadingly carwhichen'gagesfthe detent forretaining plate M2 inany desired pivotal position. The motor, by

ksuitable means such as a vbelt indicated -lcy a Adottedline, rotates apulley |46 (Fig. 6) which-is .connected to one end of a stub shaft |41,ithe other end of which is provided with avcrank'arm |40, the stub shaftbeing suitably rotatably 'journaled in the vertical pla-te IM. Thecrankarrn is provided with a counter balance M5. A connecting rod n| 5Ipivotally interconnects the crank arm and the said bar 140. As is betterseenin Fig. '1 the plates |28 and |43 present a vertical slot |52 l'foraccommodating the connecting rod.

Thus, rotation of the pulley M6 reciprocates It has been the pulley andthat a fractional horsepower inotor is entirely suitable. g Forpreventing seepage of abrasive and to prevent wearof the firing tube asit slides through the opening'of the plate |25, a suitable wipinglWasher |54 is vprovided and is preferably con- "nested to the plate|25.

It has been'indicated above that the slug olf abrasive upon leaving thering `tube enters and Thisbarre'land its immediately cooperatingyelements are supported by the front face of thev front flange H34 as bybolting and will now be described. Such bolting interconnects the ilange|04, a washer 155, a diaphragm ll, and a flange 58 of a guard tube orshell Il'al. The barrel is longitudinally movably supported within theshell i5@ and for this purpose the barrel slidingly engages aperturedguide block 62, the latter being suitably secured to the shell.

The aperture of the washer 58 is convex rearwardly and outwardly as atIM, The Washer is of a composite structure, and that portion thereofwhich is convex is made of a very tough wearresisting stiff material andthe flat body portion thereof is made of relatively ilexible material.The purpose of such composite structure will hereinafter appear.

The diaphragm ll is similar to the diaphragms l0 and is best seen inFig. 9. flat disc provided with any desirable number of slits H31 whichradiate from a central point.` As is seen in Fig. '7, when pressure isexerted on the rear face of the diaphragm the slitted portion thereofdeforms or projects forwardly and prei sents a pluralityv of lips whichenter the rear end i6@ of the firing tube. This end flares outwardly andis urged against the diaphragm by washer and spring means H0.

The operation of this alternative embodiment is as follows: e

Abrasive is supplied to the receptacle 95 through the intake lill andsubstantially cornpletely fills the former so that, when the firing tubeis in the position seen in Fig. 5,-upon appli-- cation of power, thering tubes will be driven or pushed through the abrasive so as tosegregate therefrom or cut thereoutof and completely surround andenclose a slug of abrasive. During the segregating action the abrasivedisplaced by the ring tube backs up into the expansion charnber [U2 andinto the intake. As the ring tube approaches the washer IE5, the forwardportion of the abrasive within the tube becomes somewhat packed or theindividual particles of abrasive constituting such portion become closertogether' than such particles would if the receptacle were continuous.his packing is more marked when the firing tube projects into theaperture of the washer. The firing tube moves forward until it is insealing relation with the convex surface of the washer and for insuringa good seal between the .firing tube and the Washer, the latter, due tothe nexibility of the flat outer portion thereof, may be slightlydisplaced.

Ey means of set screw ita-i the collar 33 may beso adjusted that whensuch seal is suitably established, the valve is opened by coactionbetween the arm S36 and the collar. When the valve is opened, live fluidunder high pressure rushes behind the slug in the firing tube and due toits initial pressure and expansion the slug is blown or exploded out ofthe firing tube, through the diaphragm and nally projected out of thebarrel e8. The relationship of the various elements when a slug is beingejected or fired, is seen in Fig. '7. The breech member or ringtube 95is preferably extended outside of the abrasive receptacle so that thevalve I il may be spaced a sai'e distance from the chargev in thebreech. lIhus When the breech tube has been moved forwardly to firingpostion as. shown in Fig. 7 the length of the .slug or mass in the tubedoes not extend to the valve.

While the slug is passing through the dia- Itis a phragmthe said lipsthereofv which are formed Aby the slits E51 flex forwardly into theoutwardly lips terminate also ilexes forwardly. Such flexing urges thebarrel forwardly against the tendency of the spring I'I to urge thebarrel rearwardly. Thus during each firing cycle the barrelisreciprocated within the shell iit.

Devices constructed in accordance with this invention have successfullyoperated at a speed of 500 operating cycles per minute, so that 560slugs per minute were ejected or blown out of the device. These slugs,it will be noted, are projected intermittently and ily as slugs from thebarrel to the surface to be sandblasted. Upon striking such surface theslug will disperse and scatter as if it were a snowball.

Attention is particularly directed to the suddenness with which the airpressure is released into the rear end of the firing tube. The fluid`pressure within the firing tube cannot be released except by actuationof the slug because the slug completely fills the ring tube. ln otherwords, the fluid cannot escape around the slug, but must follow theslug. Thus, a very small quantity of fluid is required for eachoperating cycle to shoot the slug. Tlu's quantity may be as small as afew cubic inches as compared to several cubic feet which is required ina conventional sandblast nozzle device having a continuous stream of airpassing through an open pipe. The ratio between small quantities of airused by my method and in my guns is as small as 1/100 part of the airfor throwing the same quantity of abrasive by a sandblast.

't is to be noted that the diaphragm lE'i forms a seal at the front ofthe receptacle E5 and that no such seal is necessary at the rear of -thereceptacle.

When the ring tube is sealed against the washer, a slug within the ringtube is completely segregated from the remainder of the abrasive withinthe receptacle and such a slug is substantially, completely and entirelyprojected, all without disturbing such remaining abrasive. The latter isuneiected and unacted upon by lluid pressure.

It is well known that the abrasive contacting parts of abrasiveprojecting devices are subject to enormous Wear. rThis is particularlytrue where the relative velocity is high. Thus, in my disclosure thefiring tube and barrel are the elements of major wear. Ey constructingthe device in sections and bolting the sections together, these elementsmay ber readily replaced. For instance, by removing the bolting whichinterconnects the elements llfi, 56, lill, and l58, the barrel, thediaphragm, the washer and the firing tube may be replaced in a veryshort period 0f time.

When devices of the character described operate at the speed describedand project the abrasive upwadly, horizontally or slightly downwardlythe diaphragm l5? may be dispensed with because the interval betweeneach cycle of operation is too short for gravity to act on the slugsufdciently to move it materially.

The alternative construction seen in Figs. 11 and l2 is similar to thatseen in Figs. 5, 6 and 7, and only the differences therebetween will bedescribed, such differences being chiey in the provision of pneumaticmeans for reciprocating the firing tube. In this alternativeconstruction compressed -uidpreferably air, recprocates a piston whichin `turn ciprocates the firing tube. As the firing tube approaches theend of its forward stroke, a valve is opened Yand admits into the firingtube the compressed fluid which has actuated the piston.

To this end a cylinder |15 is provided with. a front flange |16 and arear flange |11. An apertured bumper plate I 18 is interposed betweenanges and |16 and is suitably secured between and to these flanges as bybolting, riveting, or welding. c

The piston which reciprocates in the cylinder Ais itself a valve andcomprises .a relatively thin cylindricalshcll I 80. The front end of theshell `is interiorly threaded for receiving a base IBI which is providedwith a threaded central aperc a main source of fluid pressure |86 which,by

means of a control valve |81, communicates with an automatic valveindicated generally in Fig. 11 -by the reference character |89. Thisvalve alternately directs the fluid pressure to one-side and then theother side of the piston.v The automatic valve is seen in detail inFig.12 and comprises a casing |9| which is surrounded by a jacket |92 so asto provide a space between the casing and `the jacket.

The fluid pressure from the control valve |81 `is admitted to this spaceand bymeans of apertures |93 ows into the interior of the casing. It isto be noted that the interior |94 is cylindrical and that the holes |93are in two circumferentially extending rows,` one at each end of theinterior. The rear end of the casingthreadingly receives a hollow plug|96 which communicates withthe interior |94 and which by means of aconduit |91 communicates with thefront end of the ,cylinder |15immediately adjacent the flange |16. The inner end of the plug |496pre,- sents a valve seat which in the present instant is preferablyspherical. interconnecting the front end of the casing |94 `and the rearend of the cylinder |15 is a conduit |99, the rear `end of whichpresents a spherical valve seat.

Adapted for coaction with these valve seats and disposed within theinterior r4|94 of the casing is a ball 200, the diameter of which isVsubstantially equal to the diameter of the interior |94 so that fluidpressure vcannot pass from one of these series of apertures |93 aroundlthe ball to `the other series of apertures. These apertures are solocated vthat the ball is alwaysbe'tween them. Thus, it is seen thatwhen the ball is in the position seen in Fig. l2, fluid pressure isadmitted against the rear of the vpiston and that when the ball moves tothe left of Fig. 12 fluid pressure will be admitted against thefront ofthe piston. Y

Means will now be described for exhausting the iiuid pressure built upwithinv the cylinder |15. As was heretofore said, the fpistonhas lanopening extending longitudinally therethrough, but `it is to be notedthat such opening', by means 'of the firing tube 96, does notcommunicate with the forward portion of the cylinder |15. The piston,unless this opening is sealed, cannot be forced forwardly by Yfluidpressure. According `to this invention valve means are provided forsealing this opening and consequently, for permitting fluid pressure tobuild up behind the piston and force the same forwardly, such means alsocontrolling the admission of fluid pressure to the interior of thefiring tube 96.

This valve means, which is built into the piston, comprises a cup-likecap 202 which is vthreaded. to the base IBI and which presents anopening 293. Adapted'for seating on the rear surface of the base andconsequently for sealing the aperture 'through the piston is a plate205. Resilient means in the form of a spring 206 are interposedbetween'the p-late 205 and the cup 202 for normally maintaining theOpening closed. The `base isprovided with a Aplurality ofcircumferentially spaced openings for accommodating pins 291, the rearside of which are provided with enlarged heads. rlhe heads abut theplate v205 and serve the purpose of preventing the pins from workingtheir way forwardly out of the opening; The pins project forwardly ofthe base .I 8| and are adapted for simultaneously engaging or rbumpingthe bumper plate |18 or unseating the plate 205 and consequentlypermitting the fluid pressure at the rear of the piston to enter thering tube 96 and expand against the slug of abrasive for projecting thesame out of the barrel S8; `ien the plate 205 is unseated, the pressureat the rear end of the cylinder is less than the pressure at the frontend thereof and consequently the ball 230 will move from the positionseen'in Fig. 12 to the left thereof and seat itself against the conduit|99. Thus the flow of'fiuid under pressure from the source |85 to therear of the cylinder will be terminated and fluid under pressure will beadmitted tothe front of the cylinder.

For exhausting fluid pressure from the front of :the piston, thecylinder is provided with a series of circumferentially spaced openings208. These openings, lit will be noted, are uncovered by the piston onlywhen the latter `occupies the extreme r-ear end of the cylinder |15 andare not uncovered when the piston is in the front end of the cylinder.These openings communicate with the interior of a hollow ring 299 whichencircles .the cylinder and which communicates with the cylindricalinterior of a valve casingZI. The front end of this valve casing iscentrally bored so that the` casing has an opening extending there#through and presents a valve seat 2II which is surrounded by a coilspring 2|2. This spring urges rearwardly a piston 2|4 which is adaptedfor reciprocation within the said cylindrical interior of the Valvecasing 2|0. The piston seats onthe seat 2|| and seals the hollowinterior of .the ring 209 from the interior Kof the valve casing 2|0.Therear end of the cylindrical interior of the valve 2I0 threadinglyreceives a plug 2I6 which, in turn, threadingly receives a conduit "2|1thelatter being in communication with the rearend of the cylinder |15.

From the foregoing it will be seen that when the piston which is withinthe vcylinder |15, the former in and of itself being a valve, isactuated forwardly, the iiuid pressure so actuating this -piston is bymeans of conduit 2I1 transmitted 'to the rear of the piston 2|4 andforces the latter against the seat 2| I. When the plate 205 is un-'seatedthis pressure is released and the piston 12H is unseated landunseals or opens communication between the ring 209 and the interior ofthe valve casing 2 IQ. l

When the plate 205 is unseated, the ball 25|) moves to the left of Fig.12 and fluid pressure is admitted to the fro-nt end of cylinder |75 byconduit |21. When vthe openings 298 are uncovered the pressure in thefront of the cylinder |15 exhausts through these openings into the ring29, into the interior of the casing 2|() and out of the forward endthereof. The uncovering of the openings 298 forces the ball from theleft of Fig. 12 to the right thereof, thus sealing the piston 2|4against the seat 2H and forcing the piston forwardly.

The moving back and forth of the ball 290 is extremely rapid and due tothe unique construction and arrangement of various valves thisalternative construction is cap-able of expelling as many as 500abrasive slugs or wads per minute. The speed of operation of the deviceis dependent upon the fluid pressure admitted to the automatic valve|89.

The various elements which. comprise a device constructed in accordancewith this alternative form of the invention may be very thin and theoverall dimensions oi such a device are within the limits ofportability. The entire device appro-ximates the weight of an ordinaryportable electric drill.

The word abrasive as used herein is intended to embrace all materialswhich, when directed against a surface, have an elect thereon. Suchmaterial might be sand, metallic shot or grit, other granular material,polishing balls, such as leather pellets, or the like.

It is interesting to note that the slugs or wads of abrasive projectedby the alternative forms of this invention are substantiailycylindrical. This is because the firing tube is substantiallycylindrical. The result is a segregated elongated projectile which fliesfrom the tube nose or end iirst and strikes the surface to be abraded.

When an open air blast nozzle or a centrifugal wheel is used, theabrasive is projected as individual particles with substantially stillair in between the particles, i. e., each particle encounters its ownindependent air resistance. If No. 50 steel grit is used there areapproximately 75,500 particles per pound. With an open air blast orcentrifugal wheel there would be '75,500 different .O07 gram projectilesspaced at random from each other. It will be Iobvious that the nozzlevelocity is higher than the target velocity even though the projectingrange or ying distance is but 2 to 3 feet. The same pound of abrasivewould comprise six or less shots for the present invention. It is notdiicult'to comprehend that abrasive projected by this invention surfersbut little loss ci velocity due to air friction.

Other forms may be employed embodying the features of my inventioninstead of the one herein explained, change being made in the form orconstruction, provided the elements stated by any of the followingclaims or the equivalent of such stated elements be employed, whetherproduced by my preferred method or by Others embodying steps equivalentto those stated in the following claims.

I therefore particularly point out and distinctly claim as my invention:

1. In apparatus of the class described, a frame, an abrasive breech insaid frame, means to intermittently feed abrasive to said breech incompact slugs, a displaceable valve member to retain the abrasive insaid breech and a metering device to intermittently admit charges of airto said vbreech to expel said intermittent charges of abrasive in theform of compact slugs.

2. In apparatus of the class described, a frame, an abrasive breech insaid frame, means to intermittently feed abrasive to said breech incompact slugs, a displaceable valve member to retain the abrasive insaid breech, a metering device to intermittently admit charges of air tosaid breech to expel said intermittent charges of abrasive in the formof compact slugs and feed mechanism operated by said metering device toactuate said abrasive feeding means.

3. In apparatus of the class described adapted to project abrasive incompact slugs, a frame, an abrasive breech in said frame, a feed pipefor abrasive opening into said breech, a valve to intermittently openand close the said opening, power means to operate said valve, an airmetering device opening into said breech, a reciprocable piston .in saiddevice, power means to operate said piston in timed relation with saidvalve to admit a charge of air to said breech after a charge of abrasivehas been fed thereto.

4. In apparatus of the class described adapted to project abrasive incompact slugs, a frame, an abrasive breech in said frame, a feed pipefor supplying abrasive to the opening into said breech, a valve tointermittently open and close said opening, power means to operate saidvalve, an air metering device opening into said breech, a reciprocablepiston in said metering device, a member connecting said piston and saidvalve to operate the valve by reciprocation of the piston and powermeans to reciprocate said piston in timed relation with said valve toadmit a charge of air to said breech after a charge of abrasive has beenfed thereto in a compact slug.

5. In apparatus of the class described adapted to project abrasive incompact slugs, a frame, an abrasive breech in said frame, a feed pipefor supplying abrasive to the opening into said breech, a valve tointermittently open and close said opening-power means to operate saidvalve, an air metering device opening into saidy breech, a reciprocablepiston in said metering device, a member connecting said piston and saidvalve to operate the latter by reciprocation of the former, a source ofhigh pressure air, means actuated by said air pressure source toreciprocate said piston in timed relation with said valve( to admit acharge of air to said breech after a charge of abrasive h as been fedthereto.

6. In apparatus of the class ldescribed adapted to project abrasive incompact slugs, a frame, an abrasive breech in said frame, a feed pipefor supplying abrasive to the opening to said breech. a valve tointermittently open and close said opening, power to means to operatesaid valve, an air metering device opening into said breech, areciprocable piston in said metering device, a member connecting saidpiston and said valve to operate the latter by reciprocation of theformer, a source of high pressure air, means actuated by said airpressure to reciprocate said piston in timed relation with said valve toadmit a charge of air to said breech after a charge of abrasive had beenfed thereto, and control' mechanism to vary the proportion of air usedto operate said piston with respect to the amount of air fed to saidabrasive breech.

7. In apparatus of the class described, a frame, an abrasive breech insaid frame with a pair 0f inlet openings andan outlet opening, a barrelamaai carried by said frame coactingwi'th said outlet opening, a feedpipe for abrasive emptyinglintc one of said inlet openings, areciprocable plunger to intermittently open and close said opening andfeed abrasive to Vsaid breech in a compact slug-g an air metering devicewith a hollow cylinder opening into said other vinlet toy thebreech,=apiston reciprocable in said cylinder, means fto -re ciprocatesaid piston, adischarge passage opening in said piston to open and closethe second named inlet to said breech, land a source of-air underpressure leading to said cylinder and admitted to said breechintermittently of saiddischargefpassage. l j

B. In apparatus of the class described, a frame, an abrasive breech insaid framewitlr apairaof inlet openings vand an youtlet opening, abarrel carried by said frame coactingl with said `outlet opening, a feedpipe for abrasive emptying into one of said inlet openings,a'reciprocable plunger to intermittently open and close'said opening andfeed abrasive to said breechin acompact slug,an air metering device witha hollow cylinder opening into said other inlet to the breech, a pistonreciprocable in said cylinder, fluid intake and exhaust ports at eachendof said cylinder, an air jacket discharging to each pair ofk intakeports, an air supply source leading to said jacket, valve mechanism toregulate the amount of airia'd` `mitted to said jacket, valve` ringscarried by said piston and adapted to seal said intake and exhaustports, a discharge passage insaidpiston to open and close the secondnamed inlet to said breech, and a source of air under pressure leadingto said cylinder andmetered by` said piston discharge passage. ,n

9,. In adevice of the characterfdescribed, the combination of anabrasive` receptacle: means projecting in said receptacle 'forsegregating and packing a quantity vof abrasives@ to form a packed slug,and means 'for projecting 'the packed slug as a slug out of the device,i

10. In .apparatus adapted to project abrasive in compact unsupportedslugs against an object, a frame with a discharge passage spaced fromsaid object, an abrasive breech in said frame, positive means toforcibly feed abrasive to said breech in compact slugs, a source ofcompressed fluid under pressure and a metering device to intermittentlyadmit charges of air to said breech to expel intermittent charges ofabrasive.

1l.. In apparatus adapted to project abrasive in compact unsupportedslugs against an object, a frame with a discharge passage spaced fromsaid object, an abrasive breech in said frame, means to feed abrasive tosaid breech in compact slugs, means to retain said abrasive in saidbreech when said breech is positioned out of horizontal position, asource of compressed fluid under pressure and a metering device operatedby said air blast to intermittently admit charges of air to said breechto expel intermittent charges of abrasive against the work.

12. In apparatus adapted to discharge abrasive in relatively compactslug-s toward an object to be cleaned thereby, a frame, an abrasivebreech in said frame. positive means to deposit successive charges ofabrasive in said breech in compact slugs, to retain said abrasive in thebreech when said apparatus is tilted and a metering device to pass airunder pressure through said breech and past said retaining means todischarge abrasive from said. apparatus toward an object. f

13. In apparatus adapted to discharge abralsive in relatively compactslugs toward an .object to be cleaned thereby,l aframe, an abrasivebreech in said frame adapted toreceive a charge of abrasive to beprojected, positive `abrasive feeding means to depositsuccessive-charges of abrasive in lsaid breech, means to retain thecharge of abrasive in said breech and means to admit fluid underpressure to said breech to si'- multaneously open said retaining meansand project said abrasive `from said apparatus, and timing mechanisminterconnecting said abrasive feeding means and fluid admitting means tofeed abrasive and fluid to said breech in timedrclation to eachother. li "r 14. In apparatus adapted to 'discharge abrasive in relativelycompact slugs toward `object to be cleaned thereby, `a frame, anabrasive' breech in said frame adapted to receive a charge of abrasiveto be projected, positive abrasive feeding means to deposit successivecharges of abrasive in said breech, `means to admit fluid under pressureto said breechto project said abrasive from said apparatus, and'timingmechanism interconnecting said `abrasive feeding means and fluidadmitting means to feed abra'- sive and fluid to said breech intimed'relation toeachother. f i' 15. In abrasive, projecting apparatusthe. combinaticn of an abrasive receptacle, `.an axially reciprocablefiring tube `one end of which ris openand projects ink said receptacle,piston and cylinder'means forre'ciprocating said firing tube,l saidpistonhaving an axial opening therethrough, the-'other end of said`firing `tube being open and secured to said piston in communication withthe opening of the latter, a cap for covering and uncoveringr theAopeningof said piston,` and means adapted for; abuttinfr `one end ofsaid cylinder for actuating said capinto uncovering position wherebyfluidundcr pres-V sure from the firing tube remote side of said pistonis admitted to said ring tube for projecting abrasiveout of said `firingtube.

16, In abrasive projecting apparatus,Y the combination of an abrasivereceptacle, an axially reciprocable ring tube one end of which is openand projects in said receptacle, piston and cylinder means forreciprocating said ring tube, said piston having an axial openingtherethrough, the other end of said rng tube being open and secured tosaid piston in communication with the opening of the latter, a cap forcovering and uncovering the opening of said piston and resiliently urgedinto covering position, means for admitting fluid under pressure to theother side of said piston, and means for intermittently actuating saidcap into uncovering position.

1'7. The combination of an abrasive receptacle provided with a pair ofopenings the Surface of one of which is flexible and convex rearwardlyand outwardly, an axially movable iring tube projecting through theother of said openings, the front end of said ring tube being adaptedfor seating against said convex surface for sealing the interior of saidtube from the remainder of said receptacle, and means for admitting duidunder pressure to the rear end of said firing tube.

18. The combination of means including an abrasive receptacle providedwith a pair of openings the surface of one of which is flexible andconvex rearwardly and outwardly, an axially movable firing tubeprojecting through the other of said openings, the front end of saidfiring tube being adapted for seating against said convex surface forsealing the interior of said tube from the remainder of said receptacle,and slitted flexible pressure responsive means for sealing said one ofsaid openings.

19. The combination of an abrasive receptacle having an opening, aexible slitted washer for closing said opening, a barrel one end ofwhich flares and is adapted for circumscribing the slit of said washer,and means for admitting fluid under pressure to said receptacle wherebyabrasive within said receptacle is projected outwardly through saidopening, through said washer by displacing the slit thereof with the lipof such slit conned by said end of said barrel, and finally through saidbarrel.

20. The combination of an abrasive receptacle having an opening, aslitted resilient'washer for closing said opening, an axially movablebarrel one end of which is adapted for circumscribing the slit of saidwasher, resilient means for urging said barrel against said Washer andmeans for admitting fluid under pressure against the abrasive withinsaid receptacle whereby such abrasive is expelled through said opening,through said washer by displacing the lips of the slit thereof againstsaid end of said barrel, and nally through said barrel.

21. A method of throwing measured masses of cleaning abrasive in rapidsuccession, comprising the steps of forcing a measured amount ofabrasive through an opening into a breech chamber in a gun and thenclosing said opening and while closed releasing a sudden charge of compressed air behind the abrasive mass to expel it from the gun andrepeating the cycle of said steps in quick succession.

22. An abrasive gun for rapidly throwing separate dense charges ofabrasive and having a ring barrel and a charge holding breech, a supplymeans for bringing abrasive to the breech, coacting elements for loadinga dense measured load of abrasive from the supply into the vbreech andfor closing the breech, means responsive to the movement of saidelements for releasing a charge of compressed air behind the load onlywhile the breech is closed.

23. The combination of a gun having a nozzle and charging chamber, acompressed air supply and abrasive supply, means for mechanicallycharging the chamber while separating a measured mass of abrasive fromthe supply and for closing the chamber, valve means for suddenlydelivering a charge of compressed air to the chamber to eject the chargeof abrasive as a mass, and an interconnecting control operatingmechanism responsive to the chamber closing means to assure closing ofthe charge chamber before delivering the compressed air, and means forshutting oif the air immediately after each discharge. Y

24. A repeating abrasive slug throwing gun in cluding a firing tube anda breech load-carrying tubeymeans for relatively moving said tubesaxially, means for presenting a mass of abrasive between the tubes whenseparated whereby when moved together a measured mass of abrasive iscontained in the breech portion and isseparated from the mass and theopening between the tubes is closedto prevent escape of abrasive or air,and means responsive to the tube movement for delivering an explosivecharge of compressed air to the mass when the tubes are in said closedposition. f

25. An abrasive throwing gun having an opening breech and an ejectingpassage, a repeating mechanism for forcibly moving a mass of abrasiveinto the breech when open and thereafter closing the gun except for freemovement through the throwing passage to prevent lateral movement ofabrasive, repeating means for releasing explosive air charges throughthe passage, and timing means causing such release only when the breechis closed and whereby the mass is forcibly ejected in a dense charge,the time of air flow constituting a small fraction of the time of thecycle including the charging and closing.

NELSON J. QUINN.

